All volumes max, all outputs disconnected, retesting with balance pot centered. Input from DAC left 1.371 VAC right 1.373 VAC. Outputs on Moreplay left 5.165 VAC both and right 5.644 VAC both. At speaker binding post left 57.79 VAC and right 63.5 VAC. Only thing was 1 or 4 RCA's as output from preamp was kind of loose and was tightened.
Plug in just 2.0 R&L without sub, play music and with the pot centered and they're louder than they ever have been but volume knob at only 20% on Moreplay. Assuming it was a bad solder inspected RCA connectors under the hood and not seeing something obvious. Barely adjust pot to center the sound, not almost all the way one direction like it had been. Plug sub r&l RCA's into Moreplay outputs, turn volume back up and right channel is nowhere...unplug left channel sub output and nothing happens...unplug right sub rca and right speaker comes back strong. Swapped them and it followed the right channel sub connector to whatever side it was plugged into so I'm assuming it's stealing voltage from that channel.
There's a splitter at the sub connecting the Moreplay/stereo system and an AVR. The splitter only was on the right channel RCA and left was plugged directly into sub. Removed the splitter and everything sure seems to be working. Now even with power amp gain at lowest and volume of Moreplay at 50% it's as loud as it had gotten at peak prior.
Thanks everyone for your input, expertise, and concern trying to help me. Everyone's comments helped me understand a bit more what's going on. If some can provide a more detailed explanation of what they assume, math still not adding up, or additional concerns please reach out but thanks again! Now it's time to be worried about the volume knob can do